RCS near-far field transformation method and system based on synthetic aperture imaging

Abstract

The invention provides an RCS near-far field transformation method and system based on synthetic aperture imaging, and belongs to the technical field of communication radars. A strict RCS (radar cross section) near-far field transformation algorithm is established by utilizing the progressive property of cylindrical wave expansion of a Hankel function in a cylindrical coordinate system and combining near-field scattering data, so that the problem of errors caused by wavefront curvature in near-field measurement is solved, and the echo signal intensity of a to-be-measured target under a far-field condition can be accurately obtained. Based on multi-angle radar signal fusion and splicing of near-far field transformation results, a high-resolution scattering characteristic image of a to-be-measured target can be synthesized. According to the method, the distance coupling effect in near-field measurement is eliminated while the detail features of the target are reserved, so that the electromagnetic scattering behavior of the target under the far-field condition is reflected more truly.

Description

Technical Field

[0001] This invention belongs to the field of communication radar technology, specifically relating to a method and system for RCS near-field and far-field transformation based on synthetic aperture imaging. Background Technology

[0002] Radar Cross Section (RCS) testing is a core foundation for stealth technology and target electromagnetic property research. In both military and civilian fields, RCS testing technology plays a crucial role in the stealth design, performance evaluation, and countermeasure research of targets such as aircraft, ships, and ground equipment. It is not only an important means of analyzing target electromagnetic scattering mechanisms and verifying theoretical models and numerical simulations, but also a necessary technical support for developing stealth weapon systems with low observability and improving equipment penetration and survivability.

[0003] The essence of stealth technology lies in effectively controlling the electromagnetic scattering characteristics of a target to achieve low observability. The main approaches include: shape stealth design, which uses specific geometric configurations to guide incident electromagnetic waves in a non-threatening direction; radar-absorbing material technology, which utilizes the loss characteristics of materials to reduce reflected energy; passive cancellation technology, which achieves mutual cancellation of scattered fields through clever structural or material design; and active cancellation technology, which uses active radiation signals to cancel the target's own scattered echoes. To accurately assess the stealth performance of a target, reliable and precise RCS testing is essential to obtain its scattering data in real or simulated electromagnetic environments.

[0004] Traditional RCS testing is typically conducted in test environments that meet far-field conditions (such as outdoor far-field or compact fields), requiring the target to be illuminated by an incident plane wave to satisfy the measurement assumptions of far-field scattering. However, limitations imposed by factors such as actual site size, test environment, confidentiality requirements, and cost make it difficult to establish test environments that strictly meet far-field conditions in many cases, especially for large targets or high-frequency test scenarios. In such cases, the RCS measurements are often obtained at distances that do not meet far-field conditions, falling under the category of near-field scattering measurements. Therefore, accurately obtaining the target's far-field RCS based on near-field measurement data has become a key issue in testing technology.

[0005] Drawing upon mature theories of near-field scanning and far-field pattern transformation in antenna measurement, research on near-field and far-field transformation of radar target scattering characteristics has emerged. This theory aims to establish a mathematical relationship between the measured response of a target under near-field illumination and reception conditions and its far-field scattering response. This allows for the calculation of the far-field RCS (Radar Cross Section) satisfying the plane wave illumination assumption through close-range scanning measurements. This has significant engineering application value for achieving far-field equivalent testing in a limited space, conducting research on the near-field detection characteristics of radar seekers, and predicting the near-field response of a target based on its known far-field characteristics.

[0006] Therefore, developing high-precision and high-efficiency near-far field RCS transformation algorithms and techniques to achieve accurate reconstruction of far-field RCS based on near-field scattering measurements, and analyzing, evaluating, and correcting the sources of error in the transformation process, has become an important research direction in the field of RCS testing technology. To fundamentally solve the above problems, a novel near-far field transformation method and processing system that balances high precision and high efficiency is urgently needed. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method and system for RCS near-field and far-field transformation based on synthetic aperture imaging.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a near-field and far-field transformation method for RCS based on synthetic aperture imaging, comprising the following steps: Acquire the position information of the turntable and the target under test, and arrange several radar antennas around the target under test to transmit radar signals; The target under test receives radar transmitted signals and generates radar received signals. Based on the acquired position information of the target under test and the radar received signals, the two-dimensional imaging of the target under test and the radar echo signal of the target under test are calculated. The RCS near-field and far-field transformation algorithm is determined based on the radar echo signal of the target under test. In cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target under test is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data of the target under test, the echo signal intensity of the target under test at different observation angles in the far-field region is calculated. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. The RCS near-field and far-field transformation algorithm based on the Hankel method obtains the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and stitches the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

[0009] The target under test receives radar transmitted signals and generates radar received signals. Based on the acquired position information of the target under test and the radar received signals, the two-dimensional image of the target under test and the radar echo signal of the target under test are calculated. The method for determining the near-field and far-field transformation algorithm of RCS based on the radar echo signal of the target under test is as follows: Based on the acquired location information of the target and the radar received signal, the two-dimensional image of the target is calculated; Based on two-dimensional imaging of the target, the spatial reflectivity function of the target is inverted through two-dimensional Fourier transform; Based on the theory of spatial linear systems, a point source Green's function is introduced to describe the propagation characteristics of electromagnetic waves in space; Based on the propagation characteristics of electromagnetic waves in space, the radar echo signal of the target under near-field and far-field conditions is calculated by combining the spatial reflectivity function of the target. RCS near-field and far-field transformation algorithm based on radar echo signals of the target under near-field and far-field conditions.

[0010] The formula for calculating the two-dimensional image of the target based on the acquired position information of the target and the radar received signal is as follows:

[0011] in, Two-dimensional imaging of the target to be measured. The spatial area occupied by the target to be measured. Let be the spatial reflectivity function of the target. Let the target be any point; This refers to the time-domain signal transmitted by the radar. At the speed of light, R is the time delay of the signal traveling between the target and the observation point, and R is the distance from the target point to the observation point.

[0012] In the step of calculating the radar echo signal of the target under near-field and far-field conditions based on the propagation characteristics of electromagnetic waves in space and the spatial reflectivity function of the target, the formula for the radar echo signal of the target under near-field conditions is as follows:

[0013] The formula for the radar echo signal of the target under far-field conditions is as follows:

[0014] in, For signal wavenumber, The imaginary unit, The angle between the turntable and the coordinate axis. This is the source point position vector.

[0015] In cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data, the echo signal intensity of the target at different observation angles in the far-field region is calculated. The method for determining the RCS near-field and far-field transformation algorithm based on the Hankel method using the near-field scattering data and the echo signal intensity in the far-field region is as follows: A near-field scattering model is established in cylindrical coordinates to calculate the near-field scattering echo signal received by the target. The near-field scattered echo signal is integrated using the two-dimensional free-space Green function, and then expanded into a superposition of cylindrical wave modes using the Hankel function addition theorem, thus obtaining the expansion of the near-field scattered echo signal. Under the condition that the measurement distance is much larger than the target size, the amplitude term in the expansion of the near-field scattered echo signal is approximated in the far-field to obtain the far-field scattered echo signal. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined based on near-field and far-field scattered echo signals.

[0016] The formula for calculating the near-field scattered echo signal received by the target under test by establishing a near-field scattering model in cylindrical coordinates is as follows:

[0017] in, Let be the scattering density function of the target.

[0018] Under the condition that the measurement distance is much larger than the target size, the amplitude term in the expansion of the near-field scattered echo signal is approximated by the far-field approximation, and the formula for the far-field scattered echo signal is expressed as follows:

[0019] in, It is a Hankel function of the second kind; For order, In order to be in The azimuth of the observation point.

[0020] The Hankel-based RCS near-field and far-field transformation algorithm acquires the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and stitches the acquired near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test. The formula for obtaining the near-field and far-field transformation result of the target under test at the m-th radar antenna based on the Hankel method is expressed as follows:

[0021]

[0022] in, Azimuth The weight function, This is the number of pattern truncations.

[0023] Secondly, the present invention provides an RCS near-field and far-field transformation system based on synthetic aperture imaging, comprising: The data acquisition and radar transmission module is used to acquire the position information of the turntable and the target under test, and to arrange several radar antennas around the target under test to transmit radar signals. The first algorithm determination module is used to receive radar transmitted signals from the target under test, generate radar received signals, calculate the two-dimensional imaging of the target under test and the radar echo signal of the target under test based on the acquired position information of the target under test and the radar received signals, and determine the RCS near-field and far-field transformation algorithm based on the radar echo signal of the target under test. The second algorithm determination module is used to obtain the near-field scattering data of the target under test in cylindrical coordinates based on the RCS near-field and far-field transformation algorithm, by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function, and to calculate the echo signal intensity of the target under test at different observation angles in the far-field region based on the near-field scattering data of the target under test. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. The near-field and far-field transformation module is used for the RCS near-field and far-field transformation algorithm based on the Hankel method to obtain the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and to stitch the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

[0024] Thirdly, the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of an RCS near-field and far-field transformation method based on synthetic aperture imaging.

[0025] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a near-field and far-field transformation method and system for RCS (Radar Cross Section) based on synthetic aperture imaging. By utilizing the asymptotic properties of the Hankel function cylindrical wave expansion in cylindrical coordinates and combining it with near-field scattering data, a rigorous near-field and far-field RCS transformation algorithm is established. This solves the error problem caused by wavefront curvature in near-field measurements, enabling accurate acquisition of the echo signal intensity of the target under far-field conditions. Based on the fusion of multi-angle radar signals and the stitching of near-field and far-field transformation results, a high-resolution scattering characteristic image of the target can be synthesized. This method preserves the detailed features of the target while eliminating the range coupling effect in near-field measurements, thus more realistically reflecting the electromagnetic scattering behavior of the target under far-field conditions. Through the generation of high-resolution scattering characteristic images, the distribution and structural characteristics of the target's scattering intensity at different observation angles can be analyzed intuitively and quantitatively, providing key data and visualization tools for applications such as stealth performance evaluation, target classification and identification, and electromagnetic design optimization.

[0026] Furthermore, the proposed Hankel method, based on cylindrical wave expansion theory, is applicable to near-field RCS measurement and transformation scenarios for various complex targets, and is particularly valuable for scattering imaging of electrically large targets or complex shapes. The method has a clear workflow, can be deployed in conjunction with various radar systems, and possesses strong engineering feasibility. Attached Figure Description

[0027] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a near-field ring scattering test diagram of the target under test in this invention; Figure 3 This is a geometric distribution diagram of the near-field measurement of the target in this invention; Figure 4 This is a test diagram of the multi-transmitter multi-receiver RCS near-field and far-field transformation model based on the Hankel method in this invention; Figure 5 This is a system diagram of Embodiment 3 of the present invention. Detailed Implementation

[0028] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0029] Example 1 like Figure 1 As shown, a near-field and far-field transformation method for RCS based on synthetic aperture imaging includes the following steps: S1: Obtain the position information of the turntable and the target under test, and arrange several radar antennas around the target under test to transmit radar signals; S2: The target under test receives the radar transmitted signal and generates the radar received signal. Based on the acquired position information of the target under test and the radar received signal, the two-dimensional image of the target under test and the radar echo signal of the target under test are calculated. The RCS near-field and far-field transformation algorithm is determined based on the radar echo signal of the target under test. S3: In cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target under test is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data of the target under test, the echo signal intensity of the target under test at different observation angles in the far-field region is calculated. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. S4: The RCS near-field and far-field transformation algorithm based on the Hankel method obtains the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and stitches the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

[0030] Specifically, in S1, the position information of the turntable and the target under test is obtained, and several radar antennas are arranged around the target under test to transmit radar signals.

[0031] like Figure 2 As shown, a target is located at a turntable, with the center of the turntable at O, and P being the observation point. The distance between any point on the target and the center O of the turntable is... , recorded as The distance between point P and point P is |R|, denoted as R.

[0032] Specifically, in S2, the target under test receives the radar transmitted signal and generates the radar received signal. Based on the acquired position information of the target under test and the radar received signal, the two-dimensional image of the target under test and the radar echo signal of the target under test are calculated. Based on the radar echo signal of the target under test, the RCS near-field and far-field transformation algorithm is determined.

[0033] S21: Based on the acquired position information of the target and the radar received signal, calculate the two-dimensional image of the target; the specific formula is as follows:

[0034] in, Two-dimensional imaging of the target to be measured. The spatial area occupied by the target to be measured. Let be the spatial reflectance function of the target, representing the target's position. The intensity of signal scattering at a given location; This refers to the time-domain signal transmitted by the radar. At the speed of light, This is the time delay of the signal traveling back and forth between the target and the observation point.

[0035] S22: Based on two-dimensional imaging of the target, the spatial reflectivity function of the target is retrieved through two-dimensional Fourier transform. The spatial reflectivity function of the target is obtained through a two-dimensional Fourier transform, transforming the time-domain signal... Convert to spatial reflectivity function:

[0036] in, For radar to receive signals, This indicates taking the conjugate of the time-domain signal transmitted by the radar, where k is the signal wavenumber. The imaginary unit; This is the Fourier kernel function.

[0037] S23: Based on the theory of spatial linear systems, a three-dimensional spatial point source Green's function is introduced to describe the propagation characteristics of electromagnetic waves in space. The three-dimensional spatial point source Green's function is: The scattering of the image point is equivalent to secondary radiation, and its Green's function is: .

[0038] in, The angle between the turntable and the coordinate axis. The source point position vector, is the spherical surface area constant.

[0039] S24: Based on the propagation characteristics of electromagnetic waves in space, and combined with the spatial reflectivity function of the target, calculate the radar echo signal of the target under near-field and far-field conditions.

[0040] The radar echo signal of the target under near-field conditions is as follows: .

[0041] The radar echo signal of the target under far-field conditions is as follows: .

[0042] S25: Based on the radar echo signals of the target under near-field and far-field conditions, the range factor is approximated to different degrees to obtain an accurate far-field RCS near-far-field transformation algorithm.

[0043] Specifically, in S3, in cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target under test is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data of the target under test, the echo signal intensity of the target under test at different observation angles in the far-field region is calculated. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region.

[0044] S31: Establish a near-field scattering model in cylindrical coordinates and calculate the near-field scattering echo signal received by the target under test; like Figure 3 As shown, let the geometric center of the target be the rotation center O of the turntable, and the distance from the radar measuring antenna to the turntable center be... The measurement location is The distance from any scattering point on the target to the center of the turntable is The scattering density function of the target is: The signal wavenumber is , and The angle between the positive and negative axes is The position vector of any scattering point on the target is The near-field scattered echo signal received by the target under test is:

[0045] S32: Integrate the near-field scattered echo signal using the two-dimensional free space Green function, and expand the integrated near-field scattered echo signal into a superposition of cylindrical wave modes using the Hankel function addition theorem, to obtain the expansion of the near-field scattered echo signal.

[0046] Integrating the near-field scattered echo signal using the two-dimensional free-space Green's function:

[0047] Since the Green's function in two-dimensional space is a zero-order Hankel function, it is expanded using the Hankel function addition theorem, and the order of integration over the target and summation over each order mode is changed. Because the test distance is much larger than the target size, let... Approximately The expansion of the near-field scattered echo signal is obtained;

[0048] in, This is a Hankel function of the second kind, describing a cylindrical wave propagating outward; The summation index represents the pattern order; In order to be in The azimuth of the observation point. This represents the integration region of the target object. It is a Bessel function of the first kind, which is related to the radial distribution in cylindrical coordinates.

[0049] S33: When the measurement distance is much larger than the target size, the amplitude term in the expansion of the near-field scattered echo signal is approximated in the far-field to obtain the far-field scattered echo signal. when At that time, the far-region approximation of the Hankel function is:

[0050] Under far-field conditions, the far-field scattered echo signal can be expressed as:

[0051] in, For distance attenuation factor, yes The azimuth angle.

[0052] Substituting the previous result into the above equation, changing the order of summation and integration, and ignoring the coefficients, we get:

[0053] S34: Determine the Hankel-based RCS near-field and far-field transformation algorithm using near-field and far-field scattered echo signals.

[0054] Specifically, in S4, the near-far field transformation algorithm based on the Hankel method far-field RCS is used to obtain the near-far field transformation results of each radar antenna of the target under test at different angles, and the obtained near-far field transformation results are stitched together to synthesize a high-resolution scattering characteristic image of the target under test.

[0055] like Figure 4 As shown, the spacing between m radar antennas If the radar circulates around the target, the measured position of each radar antenna is: Therefore, the echo signal received by the m-th antenna can be expressed as:

[0056] The formula for obtaining the near-field and far-field transformation of the target at the m-th radar antenna using the Hankel method is as follows:

[0057]

[0058] in, Azimuth The weight function, This is the number of pattern truncations. Represents the truncation of a series The minimum radius that surrounds the target scattering sphere. Slightly greater than 1 to control the truncation error.

[0059] To eliminate angular errors, the near-field and far-field transformation results within each small angle are stitched together to obtain a close-range, high-resolution image of the scattering characteristics. .

[0060] Example 2 A near-field to far-field transformation system based on synthetic aperture imaging, comprising: The data acquisition and radar transmission module is used to acquire the position information of the turntable and the target under test, and to arrange several radar antennas around the target under test to transmit radar signals. The first algorithm determination module is used to receive radar transmitted signals from the target under test, generate radar received signals, calculate the two-dimensional imaging of the target under test and the radar echo signal of the target under test based on the acquired position information of the target under test and the radar received signals, and determine the RCS near-field and far-field transformation algorithm based on the radar echo signal of the target under test. The second algorithm determination module is used to obtain the near-field scattering data of the target under test in cylindrical coordinates based on the RCS near-field and far-field transformation algorithm, by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function, and to calculate the echo signal intensity of the target under test at different observation angles in the far-field region based on the near-field scattering data of the target under test. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. The near-field and far-field transformation module is used for the RCS near-field and far-field transformation algorithm based on the Hankel method to obtain the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and to stitch the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

[0061] Example 3 like Figure 5 As shown, the present invention also provides an electronic device 100 based on the RCS near-field and far-field transformation method of synthetic aperture imaging; the electronic device 100 includes a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on the at least one processor 102, and at least one communication bus 104.

[0062] The memory 101 can be used to store the computer program 103. The processor 102 implements the steps of the RCS near-field and far-field transformation method based on synthetic aperture imaging described in Embodiment 1 by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101. The memory 101 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the electronic device 100 (such as audio data), etc. In addition, the memory 101 may include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other non-volatile solid-state storage device.

[0063] The at least one processor 102 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor 102 may be a microprocessor or any conventional processor. The processor 102 is the control center of the electronic device 100, connecting various parts of the electronic device 100 via various interfaces and lines.

[0064] The memory 101 in the electronic device 100 stores multiple instructions to implement an RCS near-far field transformation method based on synthetic aperture imaging, and the processor 102 can execute the multiple instructions to achieve the following: Acquire the position information of the turntable and the target under test, and arrange several radar antennas around the target under test to transmit radar signals; The target under test receives radar transmitted signals and generates radar received signals. Based on the acquired position information of the target under test and the radar received signals, the two-dimensional imaging of the target under test and the radar echo signal of the target under test are calculated. The RCS near-field and far-field transformation algorithm is determined based on the radar echo signal of the target under test. In cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target under test is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data of the target under test, the echo signal intensity of the target under test at different observation angles in the far-field region is calculated. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. The RCS near-field and far-field transformation algorithm based on the Hankel method obtains the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and stitches the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

[0065] Example 4 If the modules / units integrated in the electronic device 100 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, and a read-only memory (ROM).

[0066] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0067] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0068] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0069] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A near-field and far-field transformation method for RCS based on synthetic aperture imaging, characterized in that, Includes the following steps: Acquire the position information of the turntable and the target under test, and arrange several radar antennas around the target under test to transmit radar signals; The target under test receives radar transmitted signals and generates radar received signals. Based on the acquired position information of the target under test and the radar received signals, the two-dimensional imaging of the target under test and the radar echo signal of the target under test are calculated. The RCS near-field and far-field transformation algorithm is determined based on the radar echo signal of the target under test. In cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target under test is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data of the target under test, the echo signal intensity of the target under test at different observation angles in the far-field region is calculated. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. The RCS near-field and far-field transformation algorithm based on the Hankel method obtains the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and stitches the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

2. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 1, characterized in that, The target under test receives radar transmitted signals and generates radar received signals. Based on the acquired position information of the target under test and the radar received signals, the two-dimensional image of the target under test and the radar echo signal of the target under test are calculated. The method for determining the near-field and far-field transformation algorithm of RCS based on the radar echo signal of the target under test is as follows: Based on the acquired location information of the target and the radar received signal, the two-dimensional image of the target is calculated; Based on two-dimensional imaging of the target, the spatial reflectivity function of the target is inverted through two-dimensional Fourier transform; Based on the theory of spatial linear systems, a point source Green's function is introduced to describe the propagation characteristics of electromagnetic waves in space; Based on the propagation characteristics of electromagnetic waves in space, the radar echo signal of the target under near-field and far-field conditions is calculated by combining the spatial reflectivity function of the target. RCS near-field and far-field transformation algorithm based on radar echo signals of the target under near-field and far-field conditions.

3. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 2, characterized in that, The formula for calculating the two-dimensional image of the target based on the acquired position information of the target and the radar received signal is as follows: in, Two-dimensional imaging of the target to be measured. The spatial area occupied by the target to be measured. Let be the spatial reflectivity function of the target. Let the target be any point; This refers to the time-domain signal transmitted by the radar. At the speed of light, R is the time delay of the signal traveling between the target and the observation point, and R is the distance from the target point to the observation point.

4. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 3, characterized in that, In the step of calculating the radar echo signal of the target under near-field and far-field conditions based on the propagation characteristics of electromagnetic waves in space and the spatial reflectivity function of the target, the formula for the radar echo signal of the target under near-field conditions is as follows: The formula for the radar echo signal of the target under far-field conditions is as follows: in, For signal wavenumber, The imaginary unit, The angle between the turntable and the coordinate axis. This is the source point position vector.

5. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 4, characterized in that, In cylindrical coordinates, based on the RCS near-field and far-field transformation algorithm, the near-field scattering data of the target is obtained by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function. Based on the near-field scattering data, the echo signal intensity of the target at different observation angles in the far-field region is calculated. The method for determining the RCS near-field and far-field transformation algorithm based on the Hankel method using the near-field scattering data and the echo signal intensity in the far-field region is as follows: A near-field scattering model is established in cylindrical coordinates to calculate the near-field scattering echo signal received by the target. The near-field scattered echo signal is integrated using the two-dimensional free-space Green function, and then expanded into a superposition of cylindrical wave modes using the Hankel function addition theorem, thus obtaining the expansion of the near-field scattered echo signal. Under the condition that the measurement distance is much larger than the target size, the amplitude term in the expansion of the near-field scattered echo signal is approximated in the far-field to obtain the far-field scattered echo signal. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined based on near-field and far-field scattered echo signals.

6. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 5, characterized in that, The formula for calculating the near-field scattered echo signal received by the target under test by establishing a near-field scattering model in cylindrical coordinates is as follows: in, Let be the scattering density function of the target.

7. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 6, characterized in that, Under the condition that the measurement distance is much larger than the target size, the amplitude term in the expansion of the near-field scattered echo signal is approximated by the far-field approximation, and the formula for the far-field scattered echo signal is expressed as follows: in, It is a Hankel function of the second kind; For order, In order to be in The azimuth of the observation point.

8. The RCS near-field and far-field transformation method based on synthetic aperture imaging according to claim 7, characterized in that, The Hankel-based RCS near-field and far-field transformation algorithm acquires the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and stitches the acquired near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test. The formula for obtaining the near-field and far-field transformation result of the target under test at the m-th radar antenna based on the Hankel method is expressed as follows: in, Azimuth The weight function, This is the number of pattern truncations.

9. A near-field to far-field transformation system based on synthetic aperture imaging, characterized in that, include: The data acquisition and radar transmission module is used to acquire the position information of the turntable and the target under test, and to arrange several radar antennas around the target under test to transmit radar signals. The first algorithm determination module is used to receive radar transmitted signals from the target under test, generate radar received signals, calculate the two-dimensional imaging of the target under test and the radar echo signal of the target under test based on the acquired position information of the target under test and the radar received signals, and determine the RCS near-field and far-field transformation algorithm based on the radar echo signal of the target under test. The second algorithm determination module is used to obtain the near-field scattering data of the target under test in cylindrical coordinates based on the RCS near-field and far-field transformation algorithm, by measuring the cylindrical wave expansion and asymptotic properties of the Hankel function, and to calculate the echo signal intensity of the target under test at different observation angles in the far-field region based on the near-field scattering data of the target under test. The RCS near-field and far-field transformation algorithm based on the Hankel method is determined by the near-field scattering data of the target under test and the echo signal intensity in the far-field region. The near-field and far-field transformation module is used for the RCS near-field and far-field transformation algorithm based on the Hankel method to obtain the near-field and far-field transformation results of each radar antenna of the target under test at different angles, and to stitch the obtained near-field and far-field transformation results to synthesize a high-resolution scattering characteristic image of the target under test.

10. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the RCS near-field and far-field transformation method based on synthetic aperture imaging as described in any one of claims 1 to 8.

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